It depends on how long you have been out of the country.
"Where the 48 Services are suspended because you have chosen not to purchase top up credit or make a chargeable use in respect of your Account for a period of 6 months, we will remove any credit on your Account after a further 2 months and credit will not be recoverable. Your service will then remain suspended for a further 5 months and can be reconnected at any time during this period. When the suspension period ends your service will be disconnected, this agreement will end and your number will be immediately lost."
So if you have not used your phone for more than 11 months, then you will need a new number. If you have not used it for 6 months, you will have to contact 48 so they can reconnect you. (You can use the link in my signiture to contact the help desk).
